To pursue high-density mounting in semiconductor devices, bare chip mounting is the ideal. However, for bare chips, quality control and handling are difficult. In answer to this, CSP (chip size package), or packages whose size is close to that of the chip, have been developed.
Of the forms of CSP semiconductor device developed, one form has a flexible substrate provided, patterned on the active surface of the semiconductor chip, and on this flexible substrate are formed a plurality of external electrodes. It is also known to inject a resin between the active surface of the semiconductor chip and the flexible substrate, in order to absorb the thermal stress.
However, in cases where resin alone is insufficient to absorb the thermal stress, another means is required.
The present invention has as its object the solution of the above described problems, and this object subsists in the provision of a semiconductor device and method of making the same, a circuit board, and an electronic instrument such that the package size is close to the chip size, and such that apart from the stress absorbing layer, thermal stress can be effectively absorbed.